Map The vapor pressure, P, of a certain liquid was measured at two temperatures,
ID: 563246 • Letter: M
Question
Map The vapor pressure, P, of a certain liquid was measured at two temperatures, T. If you were going to graphically determine the enthalpy of vaporizaton, AHvap, for this liquid, what points would you plot? The data is shown in this table. Number Number T(K)P (kPa) 225 3.32 775 To avoid rounding errors, use three significant figures in the x values and four significant figures irn the y values point 1 6.96 Number Number NOTE: Keep the pressure units in kPa point 2 Determine the rise, run, and slope of the line formed by these points rise run slope Number Number Number What is the enthalpy of vaporization of this liquid? Number J/ mol vapExplanation / Answer
We need to plot lnK on y axis and 1/T on x axis
P = 3.32
ln P = ln (3.32) = 1.19996
T = 225.0
1/T = 0.00444
point 1 is:
x = 0.00444
y = 1.19996
P = 6.96
ln P = ln (6.96) = 1.94018
T = 775.0
1/T = 0.00129
point 2 is:
x = 0.00129
y = 1.94018
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rise = (y1-y2) = 1.19996 - 1.94018 = -0.74021
rise = (X1-X2) = 0.00444 - 0.00129 = 0.00315
slope = rise/run
= -0.74021/0.00315
= -234.6817
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use
slope = - Hvap/R
= -234.6817 = -Hvap/8.314
Hvap = 1951 J/mol
Answer: 1951 J/mol